The present invention relates to an electric machine arrangement for a motor vehicle drivetrain, having a machine housing which can be fixed to a drivetrain housing, a stator which is fixed relative to the machine housing, a rotor which is mounted, concentrically with respect to the stator, within the machine housing and which has a rotor axis, wherein an air gap is defined between the stator and the rotor.
Furthermore, the present invention relates to a motor vehicle gearbox having a gearbox housing, within which there is fixed an electric machine arrangement.
Finally, the present invention relates to a method for producing an electric machine arrangement of said type.
Electric machines are suitable as drive machines for motor vehicles, for example in purely electric vehicles or in motor vehicles with a hybrid drivetrain. In the case of motor vehicles with a hybrid drivetrain, an internal combustion engine is provided as drive engine, which is normally connected by way of a gearbox to at least one driven axle. The layout within the motor vehicle is in this case substantially predefined. There are numerous possibilities for the integration of electric machines into a drivetrain of said type. In the case of drivetrains in which the electric machine is connected, for example, to an input of the gearbox, the electric machine may be arranged coaxially with respect to the crankshaft of the internal combustion engine. It is also known for an electric machine to be arranged coaxially with respect to a drive output shaft of a gearbox. It is also known for an electric machine to be arranged outside a gearbox housing and to be connected to the gearbox by way of suitable connecting means, for example by way of a traction mechanism or a spur wheel set.
If the electric machine is arranged outside the gearbox housing, the electric machine has a dedicated machine housing, within which a rotor is rotatably mounted, generally by way of two rotary bearings such as rolling bearings.
In the case of this arrangement, bearing forces are transmitted via the machine housing to a suspension of the machine housing. In this embodiment, the machine housing must be of relatively stable design.
It is alternatively also known, in the case of a hybrid drivetrain, for the electric machine to be accommodated within the gearbox housing. In this embodiment, the electric machine does not have a “dedicated” machine housing; rather, a section of the gearbox housing is designed so as to replicate a machine housing. In this case, a rotor is for example mounted rotatably relative to the gearbox housing. Bearing forces can thus be introduced directly into the gearbox housing, which must be of relatively stable design in any case.
A certain disadvantage in the case of this embodiment consists in that the correct functioning of the electric machine arrangement can be tested only after the installation of the stator and of the rotor into the gearbox. Late testing of the functionality of the electric machine during the manufacture of the hybrid drivetrain is a disadvantage, because in the event of faults, it may be necessary for the entire gearbox to be disassembled.
In the case of the connection of an electric machine arrangement with a dedicated machine housing which is arranged outside the gearbox housing, the problem of providing suitable sealing at the connection of a motor drive shaft to a gearbox element is commonly encountered. If a completely preassembled electric machine with dedicated rotor bearings is to be installed into the gearbox housing, disadvantages arise with regard to weight and costs. This is because, in this case, a multiplicity of bearings must be provided. The machine housing must be of stable design, and consequently of a high weight, even though the bearing forces are transmitted directly to the gearbox housing, which is of mechanically stable design in any case.
An example of an electric machine which is installed without a dedicated machine housing into a gearbox housing is known from document DE 10 2012 019 971 A1.
Furthermore, it is known from document DE 10 2012 024 462 A1 for an electric machine to be arranged in a gearbox housing, wherein measures are implemented which serve for an improved bearing arrangement for a wheel set arrangement and for an improved assembly process.
From document DE 10 2012 022 452 A1, it is known for a lamination pack of a stator to be provided, on the outer circumference, with grooves which serve, together with an inner circumference of a machine housing, as cooling ducts. In this case, at one axial end of the lamination pack, there may be provided cooling duct connecting means for connecting at least two cooling ducts to one another in the region of their ends so as to form a meandering arrangement. Document DE 10 2012 022 453 A1 also discloses the design of a rotor shaft as a hollow shaft, through which cooling fluid can be conducted.
Finally, document DE 1 97 21 528 A1 discloses an electric machine and a method for the installation thereof on an assembly, wherein the electric machine has a stator and a rotor. In this case, the electric machine does not have bearing means which fix the rotary rotatably relative to the stator and, in so doing, define the axis of rotation of the rotor. Instead, the electric machine has means for temporarily fixing the position of the rotor relative to the stator. In this way, the rotor can be fixed axially, radially and in a circumferential direction relative to the stator. After installation of the rotor on a gearbox shaft and after fixing of the stator to a housing, the fixing means must be released, wherein for this purpose, the rotor is displaced axially relative to the stator.